1. Field of the Invention
This invention relates to a control of a beam used in ophthalmic procedures. More particularly, this invention relates to a micromanipulation of light beams that are used for ophthalmic inspection in diagnostic procedures and for photocoagulation. Still more particularly, this invention relates to a spring-biased apparatus for controlling the position of a focused laser beam to follow directly the movement of an operator's hand during manipulation and to return the focused beam to a predetermined location such as a center in the absence of manipulation of a control member.
2. Discussion of Related Art
In medical and diagnostic procedures, as well as in other arts, the use of focused beams of light is well-known and various types of mechanisms for focusing the light beams have been developed. In the medical arts, the use of lasers and xenon-arc lamps to treat retinal detachment and to treat tumors is now well known. In either case, the surgical light beam is momentarily optically coupled into the path an ophthalmic slit lamp which is used to aim the surgical beam. The slit lamp also provides illumination for inspecting the eye through a binocular microscope. U.S. Pat. No. 3,703,176, issued Nov. 21, 1972, to Vassiliadis et al, is an example of this kind of device, and illustrates the general structure of an optometric slit lamp in FIGS. 1 and 3. As shown, a slit lamp is an instrument for examining the eye under magnification, using a microscope (generally binocular, as illustrated) and an integral source of illumination, which directs a beam of light into the eye. The particular embodiment illustrated in Vassiliadis is a special slit lamp equipped with a laser photocoagulator, but such instruments have the same general structure. It is this general structure to which this invention is directed.
Both the slit lamp and surgical beams are directed by a spring-mounted lens in this type of device. The operator moves the lens by means of a control member, such as a joystick, having a ball joined at its fulcrum and a ball joint connection to the lens mounting. This type of beam direction control has proved unsatisfactory in that, first of all, the manually-operated control member and the beam move in opposite directions and, secondly, there is a tendency for the "home" or centered position of the beam to drift due to cumulative fatigue or to unequal loading of the mounting springs for mounting the lens. The reversal of movement between the control member and the light beam produces a sensory dissonance which has made eye/hand coordination difficult for persons using such well-known surgical laser apparatus.
In the current model of such a device available from the assignee of this invention, the micromanipulator moves the beam opposite to the direction of the hand movement of the operator. Accordingly, it is an objective of this invention to provide a micromanipulator which, contrary to that available device, moves the focused beam in the same direction as the hand movement of the operator on the control member. Thus, when the control member is moved left or right along an x-axis, the focused beam also correspondingly moves left or right. Similarly, when the control member is moved up or down along the y-axis, the focused beam correspondingly moves up or down. The mounting of such a control member, or joystick, permits the operator to select any location on a grid having x and y coordinates, so that it should be understood that movement of the control member is not confined to either axis.
In such a device, it would also be advantageous for the focused beam to return to a predetermined location, such as a center of coordinates, when manual control effort has ceased. Accordingly, it is another feature of this improvement to bias the focusing device to center the beam in the absence of a control effort by the operator.
A laser beam scanning mechanism is also shown in European Patent Publication No. 0,069,987, published Jan. 19, 1983, in which an operator shifts the position of a point irradiated by a laser beam by moving a joystick control member. As described, the position of the focused beam is determined by the angle of inclination of a mirror rotatably supported about both a horizontal and vertical axis. The use of such a gimbal mechanism is described in that publication by reference to Japanese Patent Application Laid-Open No. 106144/19180. Such device apparently requires two orthogonal rotary shafts and several levers in combination. To the contrary, satisfactory horizontal and vertical positioning of a beamsplitter in the applicants' invention is achieved with a single, biased control rod.
These and other objectives and features of the invention will become apparent from the written description which follows.